Suspension and brakes - fast road

[craigjm]

Hi all, I have got myself an old mini that I intend turning into a fast road spec car. I will start a readers cars on it when it gets going. I am in the planning stage right now and I want to fit it with discs all round. I will probably use the KAD kits to do that. Few questions -

If I fit a rear beam like the KAD kit is there any benefit to that other than saving about 20kg in weight?

Has anyone fitted coil overs to their car? If I move to a beam rear I think I have no choice.

Any suggestions on coil over kits if anyone has ever used one

Any views of KAD? Is the stuff good quality? Looks like they get decent reviews

If I change to a beam on the back and rear disc conversion does that have an impact on the offset needed for the wheels?

Thanks all